Rrty06-JB-abs

Aim. To
describe rarity and elucidate its biology in a tropical mammalian Order, the
Primates

Location.Africa, Central and South America,
Asia, Madagascar.

Methods.
A review of the literature, with some additional analyses using data
from the literature. I use a variety of definitions of rarity
in order to describe it, and to investigate its biology by correlating degree
of rarity with a variety of biological traits indicative of resource use (e.g.
size of annual home range), reproductive rate (e.g. birth interval), and
specialization (e.g. number of habitat types used).

Results.
Few primate taxa occur outside the tropics, and most taxa
are rare (small geographic range size or latitudinal extent, low density, or
both). Latitudinal extent is narrower at lower latitudes in Africa and Asia, but the potential resultant packing of taxa appears
not to explain the taxonomic diversity gradient. Whilst primate species do not
show the common, positive density by range size relationship, primate genera
show a significant shallow slope, and primate
families/sub-families a strongly positive slope. Rare taxa are
specialized, but neither use more resources, nor breed
more slowly than common taxa. The correlation of rarity and specialization is
via geographic range: taxa with small ranges, or small
ranges for their density are specialized, but not taxa at low density. Common
taxa are generalized because they consist of more differently specialized
sub-taxa, not because each sub-taxon is generalized.

Main conclusions.
Most primate taxa are rare, in which case most are
presumably likely to go extinct. Rare primates are specialized, but do not
necessarily use more resources, nor breed more slowly. Specialization as an
explanation for rarity appears to work via constriction of range size, not of density.
Common primates might be common (large range size) not because sub-taxa or
individuals are generalized, but because they are composed of more sub-taxa. A
consequence could be that persistence of even common taxa will depend on
conservation of several populations scattered across the taxon's geographic
range.

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